The cylinder head gasket on my Ryobi RY30004 has blown. I cannot figure out how to remove the crankcase from the cylinder head. I have removed the three screws that fasten the crankcase to the cylinder head and the four screws that fasten the engine to the plastic starter housing. Is there something else securing the cylinder head to the crankcase? Once I get the cylinder head off and the gasket replaced, is there anything I need to be careful about regarding the rings, etc. to be sure I maintain compression? Appreciate any help.